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Area of Circle Around a Triangle

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A=π(abc4a+b+c2(a+b+c2-a)(a+b+c2-b)(a+b+c2-c))2
(a)Length of side a
(b)Length of side b
(c)Length of side c

The Area of Circle Around a Triangle calculator computes area of a circle (A) that perfectly circumscribes the outside of a triangle. .

INSTRUCTIONS: Choose units and enter the following:

  • (a) Length of Side a
  • (bLength of Side b
  • (cLength of Side c

Area of Circle Around a Triangle (A): The area is returned in square meters and the radius (r) is returned in meters.  However, these can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The formula for the Area of a circle that circumscribes a triangle (round) is: 

A=π(abc4a+b+c2(a+b+c2-a)(a+b+c2-b)(a+b+c2-c))2

where:

  • A = Area of Circle circumscribing a triangle.
  • a = length of side a
  • b = length of side b
  • c = length of side c

Note: (a+b+c)/2 is the semi-perimeter of the triangle


A triangle is a polygon with three sides, three vertices (corners), and three angles. Triangles can be classified based on the lengths of their sides and the measures of their angles as follows:

By Side Lengths:

  • Equilateral Triangle: All three sides are equal in length.
  • Isosceles Triangle: Two sides are equal in length.
  • Scalene Triangle: All three sides have different lengths.

By Angle Measures:

  • Acute Triangle: All three angles are less than 90 degrees.
  • Right Triangle: One angle is exactly 90 degrees.
  • Obtuse Triangle: One angle is greater than 90 degrees.

The sum of the interior angles of any triangle always adds up to 180 degrees. 

Triangle Calculators